Weld defect formation in FSWed coppers

This work was undertaken to explore the formation of weld defects in FSWed copper metals via both numerical and experimental approaches. The 4 mm-thick copper sheets were friction stir welded at a tool rotational speed of 710 rpm and tool translational speed of 40 mm/min. Microstructural evaluations were performed on the welded specimens. Also a 3D arbitrary Lagrangian Eulerian numerical model was developed to obtain temperature and material velocity profiles. To this aim, DEFORM-3D was implemented for developing the numerical simulation. Numerical results for temperature values showed good agreement with the recorded experimental data. They also suggest that on the advancing side (AS) of the trailing side, the pin velocity has the minimum amount (zero), and this is the main reason for the formation of tunneling cavity. Experimental results show that a force is created between the reminder of material at the joint and the rim of AS. This force causes a prong of surface material from the AS rim to penetrate into lower parts of weld. It seems that the inadequate pressure (low values of the plunge depth), inadequate surface materials, and the trapped air are the main causes for the formation of the weld defects.